PHPlot is a graph library for dynamic scientific, business, and stock-market charts. PHPlot allows PHP developers to create pie charts, bar graphs, line graphs, point graphs, etc. from a PHP application.
The PHPlot project page on SourceForge.net is the place to go for downloads, help, and more.
The PHPlot Reference Manual contains everything you need to know about PHPlot, and more. The manual is available in both HTML and PDF formats.
You can download a zip file with the HTML version of the PHPlot Reference Manual from the downloads area of the PHPlot project page.
You can read the HTML version of the manual on line here: View the PHPlot Reference Manual.
The PDF version of the manual is available here: PHPlot Reference Manual (PDF) (about 2 MB).
(Note: The online copies of the Reference Manual might be newer than the downloadable version. If so, they were generated from the Subversion sources, and might describe features that will not be available until the next release of PHPlot.)
Trick question! It is on SourceForge.net, so of course it is completely free for you to use. You can also redistribute it unmodified without restriction. For more information see the licensing files included in the distribution.